Cookie笔记

1 Cookie的创建和发送

//1、创建cookie对象
Cookie cookie = new Cookie("name","zhangsan");

//2、将cookie中存储的信息发送到客户端---头
response.addCookie(cookie);

2 Cookie的持久化

//1.1 为cookie设置持久化时间 ---- cookie信息在硬盘上保存的时间
cookie.setMaxAge(10*60);//10分钟 ---- 时间设置为0代表删除该cookie

3 什么时候携带Cookie？

//1.2 为cookie设置携带的路径
//cookie.setPath("/WEB16/sendCookie");//访问sendCookie资源时才携带这个cookie
cookie.setPath("/WEB16");//访问WEB16下的任何资源时都携带这个cookie
//cookie.setPath("/");//访问服务器下的所有的资源都携带这个cookie

4 Cookie的删除

使用同名同路径的cookie，设置时间为0，进行覆盖即可。

//删除客户端保存 name=zhangsan的cookie信息
Cookie cookie = new Cookie("name","");
//将path设置成与要删除cookie的path一致
cookie.setPath("/WEB16");
//设置时间是0
cookie.setMaxAge(0);
response.addCookie(cookie);

5  服务端如何获取客户端携带的 Cookie

package cookie;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class GetCookieServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //获得客户端携带的cookie的数据
        Cookie[] cookies = request.getCookies();
        //Cookie cookie = new Cookie("name","zhangsan");
        //通过cookie名称获得想要的cookie
        if(cookies!=null){
            for(Cookie cookie : cookies){
                //获得cookie的名称
                String cookieName = cookie.getName();
                if(cookieName.equals("name")){//name设置时候的名字 name 
                    //获得该cookie的值
                    String cookieValue = cookie.getValue();
                    System.out.println(cookieValue);
                }
            }
        }
        
    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

6 案例-显示用户的上次访问时间

1 案例分析

2 代码实现

package lastaccesstime;

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LastAccessTimeServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        //获得当前时间
        Date date = new Date();
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        String currentTime = format.format(date);
        
        //1、创建Cookie 记录当前的最新的访问时间
        Cookie cookie = new Cookie("lastAccessTime",currentTime);
        cookie.setMaxAge(60*10*500);
        response.addCookie(cookie);
        
        //2、获得客户端携带cookie ---- lastAccessTime
        String lastAccessTime = null;
        Cookie[] cookies = request.getCookies();
        if(cookies!=null){
            for(Cookie coo : cookies){
                if("lastAccessTime".equals(coo.getName())){
                    lastAccessTime = coo.getValue();
                }
            }
        }
        
        response.setContentType("text/html;charset=UTF-8");
        if(lastAccessTime==null){
            response.getWriter().write("您是第一次访问");
        }else{
            response.getWriter().write("您上次的访问的时间是："+lastAccessTime);
        }
        
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

7 Cookie_XMind总结